Did you know that over 70% of the Earth’s surface is water? Since so little makes up the Earth’s land, countries across the globe experience negative effects triggered by natural disasters like flooding. As we continue to witness growing populations and economic advancements, billions of people living by the ocean will be impacted by rising sea levels. To monitor changes which threaten coastal ecosystems, aerial bathymetric surveying is an efficient method used to collect data and measure fluctuations from seabed to land.
Using Bathymetric LiDAR to Collect Data
The nature of this aerial survey method allows for quick and efficient data collection in non-navigable waters that preclude multibeam surveys using conventional vessel-mounted systems. These include shallow waters, rivers and streams, and areas with in-water debris and obstructions. These datasets can be readily utilized for monitoring coastal erosion, post-natural disaster coastal infrastructure damage, and the movement over time of dynamic natural bathymetric features such as sandbars.
Measuring water depth for nautical purposes dates back centuries. As technology evolved, remote sensing and mapping of shallow water became more available with bathymetric LiDAR and the help of airborne systems. The LiDAR point cloud data can additionally be paired with co-flown imagery, creating a powerful dataset containing 3D points as well as georeferenced high-resolution aerial imagery, valuable for benthic habitat mapping. Seamless digital elevation models (DEMs) can be created from the dataset incorporating both topographic features and bathymetric returns, allowing for a greater understanding of, for example, water movement during storm surges and flood modelling.
Bathymetric surveys give us an advanced means by which to measure water depth, map underwater terrain, and classify submerged vegetation and habitat just to name some of this technology’s applications.
Green and Near-Infrared Beam
The sensors used for these projects work on the married function of two differently-coloured laser channels: a green and a near-infrared beam. The near-infrared channel surveys topographic features and any on-water objects but is stopped short at the water’s surface by the rapid absorption of the short wavelength in water. This gives us a measured water surface by which to calculate depths of bathymetry, which are detected by the green channel of the laser; these longer wavelengths can penetrate water and scatter off in-water submerged objects, aquatic vegetation, and the bottom itself. The use of this technology is dependent on water quality: water turbidity dictates how deeply the laser’s light can move through the water column. Suspended sediments or algae blooms and the like will block the light from travelling into the water; the efficacy of this method of survey is referenced to the Secchi depth and/or the diffuse attenuation coefficient observed in the target water body.
Leading Edge Geomatics was an early adopter of bathymetric LiDAR. We partnered with the Advanced Geomatics Research Group (AGRG) to use the Chiroptera II. Chiroptera II is an innovative topo-bathymetric LiDAR system which simultaneously captures topographic and bathymetric LiDAR data and high-resolution imagery. We currently own and operate a Riegl 880-G2 topobathymetric sensor. Our LiDAR sensors can collect data and water depth of up to 25m deep. By using bathymetric LiDAR, we can map underwater terrain at a fraction of the cost while producing higher quality results. Due to the remoteness of many coastlines, this is often the only economically viable option for large-scale bathymetric mapping at high resolution.
Bathymetric LiDAR is a valuable tool in the modern survey toolbox. Leading Edge Geomatics runs cutting-edge sensors allowing for optimal data acquisition and product development for our clients. With a portfolio spanning a variety of aquatic zones across the Western hemisphere, we are well equipped to provide Bathymetric solutions which help clients monitor damage, mitigate future risks, plan for rehabilitation, and prepare for future events.
To learn more about our solutions, contact us today to speak with our experienced Bathymetric team.